The invention relates to an air bag for a motor vehicle having catch straps which are located on the inside and by means of which an upper bag surface directed towards a vehicle occupant and a lower-lying bag surface of the unfolded air bag having an opening for a gas generator are held against one another along the length of the catch straps.
In U.S. Pat. No. 5,165,716, an air bag is described which consists of two bag surfaces, lying one above the other and sewn together at the edge, and whose catch straps are sewn at both ends in each case onto a connecting part made of material, after which each connecting part is sewn to one of the two bag surfaces. The seam selected for this connection to the bag surface differs from the customary circular seam and is disposed in each case perpendicular to the longitudinal axis of the catch straps in order, as a result, to obtain a more favorable loading pattern of the material by the catch straps. This seam, which can only be made on a sewing machine in a complicated manner, is firstly carried out on each flat-lying bag surface. Subsequently, the bag surfaces have to be sewn to one another on the circumference with their outsides located opposite one another, after which the air bag is inverted so that the circumferential edges come to rest on the inside. Consequently, in the execution of the circumferential seam, in this case the integral catch straps which have already been sewn onto their connecting parts at both ends lie around the outside of the bag surfaces, thus making the sewing operation more difficult. Later fixing of the catch straps to the respective connecting part would be impeded by its fixing seam.
U.S. Pat. No. 5,033,771 shows an air bag in which only the seams for fixing the connecting parts are carried out perpendicular to the extent of the catch straps. The seams for fixing the catch straps are made on a circular arc above the latter, as a result of which, when force is introduced, punctiform load peaks can occur. These catch straps are likewise integral.
An air bag for a vehicle is known from British Patent Document GB-B-1,438,032, in which catch straps define the shape of the inflated air bag. The catch straps extend integrally from an attachment plate which is sewn onto the air bag. With an attachment seam which is closed in the manner of a circle, under tensile loading of the catch straps the latter are loaded very differently over their course, in which case a section which is subjected to greater loading can give way and the connection may be torn open at this point.
From the prior art which is quite comprehensive in this sector, reference is made to the following publications concerning the general background: German Patent Document DE-C-2,152,902, U.S. Pat. No. 3,618,979 and U.S. Pat. No. 3,945,665.
An object of the invention is to simplify the production of an air bag of the general type. This object is achieved by providing an air bag arrangement wherein the catch straps adjoin flat connecting parts via which they are fixed on the upper and lower bag surface by means of at least one connecting seam which extends around the respective connecting part, a connecting seam lying nearest to the catch straps being disposed perpendicular to the pulling direction of said catch strap in the region of each catch-strap connection over at least the greatest part of the connection width, and wherein the catch straps are subdivided into two parts in their length and each catch-strap part integrally adjoins a respective assigned flat connecting part.
The fixing of the catch straps via a connecting part constructed integrally therewith by sewing to the upper bag surface, the connecting seam lying nearest to the catch straps in the region of each catch-strap connection being disposed, at least over the greatest part of the connection width, perpendicular to the pulling direction of said catch strap, leads to an even loading of this connection under the effect of tension via the catch straps which, when the air bag is filled, are brought into an extended position which holds the bag surfaces against one another.
This improved course of the seam can likewise be used for such a fixing of the catch straps on the lower-lying bag surface, for which reason the catch straps are then designed in two parts in their length so that firstly the connecting parts are-sewn onto their flat-lying bag surfaces and the two halves of each catch strap are only joined together after the bag surfaces have been connected to one another.
This subdivision of each catch strap should preferably be carried out nearer to the lower-lying bag surface since the opening for the gas generator is provided here, through which opening the catch-strap halves or parts can be pulled outwards and sewn. By means of this division, a sufficient length is provided for both catch-strap parts when being pulled through the opening, and the overlap at their connecting seam does not lie precisely on the central folding point of the catch straps when the air bag is folded together, thus not unnecessarily increasing the folding height of the air bag.
In the case of three catch straps being provided, arranged approximately evenly, the course of the seam is advantageously designed as a hexagon, as a result of which the seam can lie disposed in each case in the region of each catch-strap connection, and the flat connecting part is held around the outside of the bag surface. Changes in direction in this seam are preferably to be carried out in a rounded manner in order to counteract the material tearing out at a corner.
On the lower-lying connecting part, the connecting seam is protected by a metal heat guard against the effect of temperature due to the gases flowing against it from the gas generator, as a result of which said connecting seam can also be used for attaching a flame-proof material which protects the surroundings of the gas generator inside the bag.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.